OBJECTIVES: 1. We propose the measurement of oxygen partial pressure in the arterial wall in vivo, since relatively few such measurements have been reported even though hypoxia has been implicated in the potentiation of atherosclerosis. 2. We propose an examination of the interaction of the various factors involved in the "resistance" to oxygen transport to and within the avascular layer of the wall under various geometric conditions, which include the oxygen transfer coefficient from the blood, the diffusion coefficient of the wall, and the diffusion distance, all in relationship to oxygen consumption: previous experience suggests an alteration of these relationships during carbon monoxide inhalation and our analyses suggests a relative reduction in oxygen availability in the areas of certain flow perturbations subject to the development of early atherosclerosis. 2. Therefore, in addition to the in vivo studies, we propose the programming and carrying out of the numerical solution of the conservation principals of fluid dynamics and diffusing oxygen molecules for pulsatile flow, because the coupled relationshop between convection and diffusion in the lumen and in the avascular wall portion of arteries is not well understood. In vivo measurements from areas of defined geometry will be used as "scaling factors" for this program, permitting generalization to other locations.